In general, a polyol compound such as a polyether polyol is produced by ring-opening addition polymerization of an alkylene oxide selected from e.g. ethylene oxide and propylene oxide, with an initiator having active hydrogen atoms. A polyol compound like this polyether polyol is used as a material for a functional lubricant or a polyurethane product such as a polyurethane elastomer, an elastic fiber, an adhesive agent or a sealant. The physical properties or mechanical properties of the polyurethane product or functional lubricant made from the polyether polyol as a material, may be influenced by the properties of the polyether polyol, such as the intermolecular force, crystallinity, hydrophilicity, solvent resistance, heat resistance and weather resistance. Therefore, a technique is used to modify the polyether polyol to adjust the properties. As such a technique, there is, for example, a method wherein a polyester polyol, a polycarbonate polyol or a polyoxytetramethylene glycol is used as an initiator, and with the initiator, an alkylene oxide is polymerized in a block form by ring-opening addition polymerization, to obtain a polyester ether polyol, a polycarbonate ether polyol or a polyether polyol. Also proposed is a method for producing a polyester ether polyol or a polycarbonate ether polyol, which contains, in its polyether main chain, ester bonds or carbonate bonds at random, or polyester chains or polycarbonate chains in a block form.
They may be used as materials for polyurethane products.
As a method for producing a polyester ether polyol having ester bonds in the main chain, a method for ring-opening addition polymerizing a cyclic ester compound (lactone) with a polyol initiator by using a tin-based catalyst to obtain a block copolymer having a narrow molecular weight distribution (e.g. Patent Document 1), or a method for ring-opening addition polymerizing an alkylene oxide and the cyclic ester compound by using an alkali metal compound catalyst to obtain a random copolymer (e.g. Patent Document 2), is reported.
However, if a block copolymer obtained by ring-opening addition polymerization of a cyclic ester with a polyol initiator by using the above tin-based catalyst, is reacted with a polyisocyanate to obtain a prepolymer, and the prepolymer is further reacted with a chain extender and/or a curing agent to obtain a polyurethane elastomer, such a polyurethane elastomer has a low tensile strength and its heat resistance is not high. Further, a polymer obtained by randomly copolymerizing an alkylene oxide and a cyclic ester compound by using the above alkali metal compound catalyst, has a high viscosity, and yet it is difficult to remove the alkali metal compound catalyst from the polymer, whereby there may be a problem such that ester bonds are easily hydrolyzed by the remaining catalyst.
Further, it is reported that a homopolymer of ε-caprolactone, and a random copolymer or a block copolymer of ε-caprolactone and propylene oxide may be obtained in the presence of double-metal cyanide complex catalysts containing glymes such as ethylene glycol dimethyl ether, diethylene glycol dimethyl ether and triethylene glycol dimethyl ether, as organic ligands (e.g. Patent Document 3). However, the double-metal cyanide complex catalysts used here do not have a high activity for ring-opening polymerization of a cyclic ester compound, so it is necessary to use a large amount of the catalyst for ring-opening addition polymerization of the cyclic ester compound. Therefore, a process step for removing the catalyst from the obtained copolymer will be necessary. Moreover, in this process, a polymerization solvent such as THF is used to make the molecular weight distribution of the obtainable copolymer to be narrow. Consequently, a process step for removing the polymerization solvent from the final product will be essential. In addition, since the reaction is carried out at a low temperature, there will be problems such that the ring-opening polymerization rate of the cyclic ester will be slow, and the productivity will be low.
Patent Document 1: JP-A-10-072516 (U.S. Pat. Nos. 6,008,312 and 6,103,852)
Patent Document 2: JP-A-2004-515586 (U.S. Patent Publication 2004-68091)
Patent Document 3: U.S. Pat. No. 5,032,671